I am looking for information on the model 8502 high purity change over manifold. on line specs offer an annunciator, which requires 120 v power. What is the annunciator? A lignt? A bell? A horn? I would like to spec a contact closure to be provided in addition to/in lieu of the annunciator. Remote alarm will be much more beneficial than the annunciator. What is the electrical connection required. Does the unit come w/ a plug that can plug into a convenience outlet? Or does it want to be hard wired into a dedicated circuit? Thanks Randy